Test an O2 sensor - Page 2 - JeepForum.com

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post #16 of 22 Old 04-19-2011, 05:08 PM Thread Starter
scifone
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I tested the O2 sensor per the FSM and it came back reading about 3.2 ohms. Does that mean it needs to be replaced?

I also installed a manifold from 1AAuto and that thing went on super easy. I didn't even have to use PB. I was able to see the crack in the old manifold and it was pretty bad. There was a crack about half way around one of the tubes. The engine is much more quiet.

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post #17 of 22 Old 04-19-2011, 07:27 PM
Nibbley15
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Quote:
Originally Posted by scifone View Post
I tested the O2 sensor per the FSM and it came back reading about 3.2 ohms. Does that mean it needs to be replaced?

I also installed a manifold from 1AAuto and that thing went on super easy. I didn't even have to use PB. I was able to see the crack in the old manifold and it was pretty bad. There was a crack about half way around one of the tubes. The engine is much more quiet.
That was just testing the heating element of the O2 sensor, should be between 5-7; infinity reading is bad. So unless you pull the voltage test, or getting a code from the computer then I say run it IMHO.

I had the same crack in my manifold, I was able to get away with just welding it, but it doesn't always work (sometimes you chase the crack). Glad to hear it is working well. Have to get some miles on there and see how the mileage goes.
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post #18 of 22 Old 08-16-2013, 01:58 AM
The_Goob
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Originally Posted by JOExFROMxNY View Post
From the 1994 Wrangler / Cherokee FSM. see if these help:
I hate to necro this thread, I got a reading of 0.8 ohms following this chart. Does that mean it's toast?
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post #19 of 22 Old 08-16-2013, 08:19 AM
jsipe007
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Just a quick FYI, if you suspect a faulty O2 sensor and test appear to be inconclusive, you can get a new Bosch O2 sensor for around $20 from rockauto. I just replaced mine, it had 133,000 miles on it.
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post #20 of 22 Old 08-16-2013, 10:12 AM
Que89YJ
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O2 sensor heater should have 3-5 ohms(2 white wires). The signal line output to the ecu should be a voltage dc reading after it warms up (Usually within 30 seconds after start). The voltage output should be between 0-1vdc. normally around .4 volts.
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post #21 of 22 Old 08-16-2013, 05:52 PM
pete1991YJ
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Originally Posted by Que89YJ View Post
O2 sensor heater should have 3-5 ohms(2 white wires). The signal line output to the ecu should be a voltage dc reading after it warms up (Usually within 30 seconds after start). The voltage output should be between 0-1vdc. normally around .4 volts.
X2 I was just gonna say that... instead, I'll copy-paste my old post:

" I prefer NAPA or Bosch (if available). FWIW the O2 sensor is pretty easy to remember: You should roughly see between 3/10 of a volt (300mV) and about 8/10 of a volt (800mV) on the sense wire depending on warm-up and running conditions. It should vary over time with temperature, throttle opening, etc."


BTW this applies to pretty much all O2 sensors.

***--- Wrecking Crew member ---***
"I've prolly been around longer than you think"
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post #22 of 22 Old 08-16-2013, 08:20 PM
JWELK
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There is a youtube video on checking them. Basically remove the sensor and clamp it into a vise. There are either 1 or 3 wires. If 3 wires it is heated, put one meter lead on the odd colored lead, the other lead to the chassis of the sensor. Set the voltmeter to low voltage, if you go to ohms you will destroy the unit. Then heat the business end with a torch, the voltmeter should read just under 1 volt if it is good. In the video, the sensor is heat to red hot. The sensor makes a comparison between inside and outside O2. Make certain the outside vent is not clogged.

Regards,

Jim W
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